A method for preparing copper-based nanomaterials rich in two-dimensional defects and their application in electrocatalytic CO2 reduction.

Abstract

This invention discloses a method for preparing copper-based nanomaterials rich in two-dimensional defects and their application in electrocatalytic CO2 reduction. The method involves inducing two-dimensional defects in the copper-based nanomaterials through halogen (F, Cl, Br, and I) doping during electrochemical deposition, thereby obtaining copper-based nanomaterials rich in two-dimensional defects. This invention, through electrochemical deposition, effectively incorporates halogen elements into copper nanomaterials, inducing different defects and active sites, enhancing the adsorption capacity of reaction intermediates, and improving the conversion of carbon dioxide (eCO2RR) to more carbon (C) atoms. 2+ The conversion efficiency of the product can be affected, and the type and size of defects can also be changed by adjusting the type and concentration of halides in the electrolyte.

Description

Technical Field

[0001] This invention relates to the fields of materials science and electrocatalysis, specifically to a method for preparing copper-based nanomaterials rich in two-dimensional defects by doping with halogen elements. Background Technology

[0002] With industrialization, the excessive consumption of fossil fuels has led to a continuous increase in atmospheric CO2 accumulation, resulting in environmental problems and an energy crisis. Combining electrocatalytic carbon dioxide reduction reactions with renewable energy sources to produce value-added fuels and chemicals is a potential strategy for achieving a carbon-neutral energy cycle. Copper-based catalysts possess a unique ability to convert CO2 into multi-carbon products, exhibiting high activity and selectivity.

[0003] The activity and selectivity of copper-based catalysts can be tuned through defect engineering. Introducing defects into copper can generate a large number of active sites for the adsorption of reactants and reaction intermediates. Introducing various two-dimensional defects (grain boundaries, twin boundaries, and stacking faults, etc.) into copper through chemical and electrochemical methods can lower the free energy barrier of intermediates during CO2 reduction. Doping non-metallic heteroatom halogens into the Cu lattice can induce lattice mismatch and dislocations on the Cu surface, generating a large number of two-dimensional defects. The content of the doped halogen also affects the type and size of defects in Cu. During electrochemical reduction reactions, halogen-doped metal oxide catalysts tend to undergo structural evolution and compositional changes at the cathode potential. This electrochemical reconstruction process can induce multiple defect active sites on the Cu surface, which is beneficial for the adsorption and stabilization of reaction intermediates, thereby enhancing the performance of eCO2RR. Although there are many reported studies on copper surface doping with halogens, a one-step electrochemical deposition method for doping has not been previously reported. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing copper-based nanomaterials rich in two-dimensional defects. By doping halogen elements during the electrochemical deposition process and controlling the concentration of halides in the electrolyte, more defects and active sites are obtained, thereby achieving high selectivity and stability in the electrocatalytic carbon dioxide reduction reaction (eCO2RR).

[0005] To achieve its objectives, the present invention employs the following technical solution:

[0006] A method for preparing copper-based nanomaterials rich in two-dimensional defects is characterized by: in the process of preparing copper-based nanomaterials by electrochemical deposition, halogen doping is used to induce the formation of two-dimensional defects in the copper-based nanomaterials to obtain copper-based nanomaterials rich in two-dimensional defects.

[0007] Furthermore, the two-dimensional defects include twin boundary defects (TB), stacking fault defects (SF), and grain boundary defects (GB). The type of two-dimensional defect formed can be controlled by adjusting the type of halogen used for doping. F doping induces the formation of twin boundary defects and stacking fault defects in copper-based nanomaterials, Cl doping induces the formation of stacking fault defects in copper-based nanomaterials, and Br doping or I doping induces the formation of grain boundary defects in copper-based nanomaterials.

[0008] Furthermore, the preparation method of the copper-based nanomaterial rich in two-dimensional defects specifically includes the following steps: in an electrolytic cell with two electrodes, high-purity copper foil is used as the anode and carbon paper as the cathode, and potassium hydroxide solution with added halides is used as the electrolyte. A current of 170-210 mA is applied, and the reaction is carried out for 0.5-1 hour. Then, the carbon paper is removed, cleaned, and dried to obtain the copper-based nanomaterial rich in two-dimensional defects.

[0009] Preferably, the concentration of the potassium hydroxide solution is 1.0–4.0 mol / L.

[0010] Preferably, the concentration of halides in the electrolyte is 0.1–1.0 mol / L. Specifically, the halides may be NH4F, NH4Cl, NH4Br, or NH4I.

[0011] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0012] 1. This invention utilizes an electrochemical deposition process to effectively incorporate halogen elements into copper nanomaterials, inducing different defects and active sites, enhancing the adsorption capacity of reaction intermediates, and improving the eCO2RR conversion to C 2+ The conversion efficiency of the product can be affected, and the type and size of defects produced can also be changed by adjusting the type and concentration of halides in the electrolyte.

[0013] 2. The copper-based nanomaterials rich in two-dimensional defects obtained in this invention are grown in situ on carbon paper and can be directly used as gas diffusion electrodes for the electrocatalytic reduction of CO2, realizing the conversion of CO2 to C at room temperature. 2+ High-performance conversion of products. For example, the local current density of ethylene at -1.74V vs. RHE using an I-doped Cu electrode can reach 273.3 mA / cm². 2 The corresponding Faraday current efficiency is 68.13%, and it has high selectivity and stability.

[0014] 3. This invention uses electrochemical deposition to dope halogen atoms onto the copper surface, thereby creating numerous defects and active sites on the copper surface, facilitating the reduction of carbon dioxide to C. 2+ The product creates favorable conditions, the method is novel and simple to operate, and the resulting copper-based nanomaterials rich in two-dimensional defects have controllable morphology and uniform size. Attached Figure Description

[0015] Figure 1 This is a SEM image of the copper nanoparticles prepared in Example 1 at a current of 170 mA.

[0016] Figure 2 This is a SEM image of the copper nanoparticles prepared under a current of 190 mA in Example 2.

[0017] Figure 3 This is a SEM image of the copper nanoparticles prepared in Example 3 at a current of 210 mA.

[0018] Figure 4 TEM image of the F-doped copper-based nanomaterial prepared in Example 4. Figure 4 (a) and HRTEM diagram ( Figure 4 (b) and (c)).

[0019] Figure 5 TEM image of the Cl-doped copper-based nanomaterial prepared in Example 5. Figure 5 (a) and HRTEM diagram ( Figure 5 (b) and (c)).

[0020] Figure 6 TEM image of the Br-doped copper-based nanomaterial prepared in Example 6. Figure 6 (a) and HRTEM diagram ( Figure 6 (b) and (c)).

[0021] Figure 7 TEM image of the I-doped copper-based nanomaterial prepared in Example 7 ( Figure 7 (a) and HRTEM diagram ( Figure 7 (b)(c)).

[0022] Figure 8 XRD patterns of copper nanoparticles prepared in Example 2 and halogen-doped copper-based nanomaterials prepared in Examples 4-7.

[0023] Figure 9 The Faraday efficiency diagrams are shown for the copper nanoparticles prepared in Example 2 and the halogen-doped copper-based nanomaterials prepared in Examples 4-7, during the electrocatalytic CO2 reduction of ethylene, a product of the process.

[0024] Figure 10 The current density diagrams show the ethylene product obtained during the electrocatalytic CO2 reduction process of the copper nanoparticles prepared in Example 2 and the halogen-doped copper-based nanomaterials prepared in Examples 4-7. Detailed Implementation

[0025] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to examples. The following content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific examples described, or use similar methods to replace them, as long as they do not depart from the inventive concept or exceed the scope defined by the claims, and all such modifications and additions should fall within the protection scope of the present invention.

[0026] Example 1

[0027] In this embodiment, copper nanoparticles grown in situ on carbon paper were prepared according to the following steps:

[0028] In a two-electrode electrolytic cell, high-purity copper foil measuring 2 mm × 2 mm and carbon paper measuring 2 mm × 2 mm were used as the anode and cathode, respectively, with a distance of 2 cm between the two electrodes. A 3.0 mol / L potassium hydroxide solution was used as the electrolyte, and a constant current of 170 mA was applied under a DC power supply for 0.5 hours.

[0029] After the reaction is complete, the cathode is removed, washed with deionized water, and then dried with a spray gun containing N2 to obtain carbon paper with deposited copper nanoparticles.

[0030] Example 2

[0031] In this embodiment, copper nanoparticles grown in situ on carbon paper were prepared according to the following steps:

[0032] In a two-electrode electrolytic cell, high-purity copper foil measuring 2 mm × 2 mm and carbon paper measuring 2 mm × 2 mm were used as the anode and cathode, respectively, with a distance of 2 cm between the two electrodes. A 3.0 mol / L potassium hydroxide solution was used as the electrolyte, and a constant current of 190 mA was applied under a DC power supply for 0.5 hours.

[0033] After the reaction is complete, the cathode is removed, washed with deionized water, and then dried with a spray gun containing N2 to obtain carbon paper with deposited copper nanoparticles.

[0034] Example 3

[0035] In this embodiment, copper nanoparticles grown in situ on carbon paper were prepared according to the following steps:

[0036] In a two-electrode electrolytic cell, high-purity copper foil measuring 2 mm × 2 mm and carbon paper measuring 2 mm × 2 mm were used as the anode and cathode, respectively, with a distance of 2 cm between the two electrodes. A 3.0 mol / L potassium hydroxide solution was used as the electrolyte, and a constant current of 210 mA was applied under a DC power supply for 0.5 hours.

[0037] After the reaction is complete, the cathode is removed, washed with deionized water, and then dried with a spray gun containing N2 to obtain carbon paper with deposited copper nanoparticles.

[0038] Figures 1-3 The images show SEM images of the copper nanoparticles prepared in Examples 1 to 3. As can be seen from the images, the products are irregularly stacked nanoparticles, even stacked into spherical structures, with particle sizes ranging from 100 to 500 nm.

[0039] Example 4

[0040] In this embodiment, F-doped copper-based nanomaterials rich in two-dimensional defects were prepared according to the following steps:

[0041] In a two-electrode electrolytic cell, high-purity copper foil (2 mm × 2 mm) and carbon paper (2 mm × 2 mm) were used as the anode and cathode, respectively, with a distance of 2 cm between the electrodes. A 1.0 mol / L potassium hydroxide solution with 0.1 M NH4F was used as the electrolyte, and the reaction was carried out for 1 hour under a constant current of 190 mA using a DC power supply. After the reaction was complete, the carbon paper deposited on the cathode was removed, rinsed several times with deionized water, and then dried using a spray gun loaded with N2, thus obtaining F-doped copper-based nanomaterials rich in two-dimensional defects.

[0042] Figure 4 TEM image of the F-doped copper-based nanomaterial prepared in this embodiment. Figure 4 (a) and HRTEM diagram ( Figure 4 As shown in (b) and (c), the F-doped copper-based nanomaterials contain a large number of twin boundary defects and stacking fault defects.

[0043] Example 5

[0044] In this embodiment, Cl-doped copper-based nanomaterials rich in two-dimensional defects were prepared according to the following steps:

[0045] In a two-electrode electrolytic cell, high-purity copper foil (2 mm × 2 mm) and carbon paper (2 mm × 2 mm) were used as the anode and cathode, respectively, with a distance of 2 cm between the electrodes. A 2.0 mol / L potassium hydroxide solution with 0.3 M NH4Cl was used as the electrolyte, and the reaction was carried out for 1 hour under a constant current of 190 mA using a DC power supply. After the reaction was complete, the carbon paper deposited at the cathode was removed, rinsed several times with deionized water, and then dried using a spray gun loaded with N2, thus obtaining Cl-doped copper-based nanomaterials rich in two-dimensional defects.

[0046] Figure 5 TEM image of the Cl-doped copper-based nanomaterial prepared in this embodiment. Figure 5 (a) and HRTEM diagram ( Figure 5As shown in (b) and (c), the Cl-doped copper-based nanomaterials contain a large number of stacking fault defects.

[0047] Example 6

[0048] In this embodiment, Br-doped copper-based nanomaterials rich in two-dimensional defects were prepared according to the following steps:

[0049] In a two-electrode electrolytic cell, high-purity copper foil (2 mm × 2 mm) and carbon paper (2 mm × 2 mm) were used as the anode and cathode, respectively, with a distance of 2 cm between the electrodes. A 3.0 mol / L potassium hydroxide solution with 0.5 M NH4Br was used as the electrolyte, and the reaction was carried out for 1 hour under a constant current of 190 mA using a DC power supply. After the reaction was complete, the carbon paper deposited on the cathode was removed, rinsed several times with deionized water, and then dried using a spray gun loaded with N2, thus obtaining Br-doped copper-based nanomaterials rich in two-dimensional defects.

[0050] Figure 6 TEM image of the Br-doped copper-based nanomaterials prepared in this embodiment. Figure 6 (a) and HRTEM diagram ( Figure 6 As shown in (b) and (c), the Br-doped copper-based nanomaterials contain a large number of grain boundary defects.

[0051] Example 7

[0052] In this embodiment, I-doped copper-based nanomaterials rich in two-dimensional defects were prepared according to the following steps:

[0053] In a two-electrode electrolytic cell, high-purity copper foil (2 mm × 2 mm) and carbon paper (2 mm × 2 mm) were used as the anode and cathode, respectively, with a distance of 2 cm between the electrodes. A 4.0 mol / L potassium hydroxide solution with 1.0 M NH4I was used as the electrolyte, and the reaction was carried out for 1 hour under a constant current of 190 mA using a DC power supply. After the reaction was complete, the carbon paper deposited on the cathode was removed, rinsed several times with deionized water, and then dried with a spray gun loaded with N2, thus obtaining I-doped copper-based nanomaterials rich in two-dimensional defects.

[0054] Figure 7 TEM image of the I-doped copper-based nanomaterial prepared in this embodiment. Figure 7 (a) and HRTEM diagram ( Figure 7 As shown in (b) and (c), it can be seen from the figure that the I-doped copper-based nanomaterial contains a large number of grain boundary defects.

[0055] To verify the performance of the electrodes obtained in the above embodiments for the electrocatalytic reduction of CO2, the following tests were conducted: In a flow reactor with a three-electrode system, carbon paper with deposited copper nanoparticles obtained in Example 2 was used as the working electrode, or halogen-doped copper-based nanomaterials obtained in Examples 4, 5, 6, and 7 were used as the working electrode. Ni was used as the counter electrode, Ag / AgCl as the reference electrode, and 1.0 mol / L potassium hydroxide solution was used as the anode and cathode electrolytes. CO2 was introduced into the cathode electrolyte at a flow rate of 30 sccm, and a voltage of -0.4 V vs. RHE or higher was applied. The products were quantitatively analyzed using gas chromatography and nuclear magnetic resonance spectroscopy.

[0056] Figure 9 and Figure 10 The figures show the Faradaic efficiency and current density of ethylene, the product obtained during the electrocatalytic reduction of CO2. As can be seen from the figures, the local current density of ethylene on the I-doped Cu electrode reaches 273.3 mA / cm² at -1.74 V vs. RHE. 2 The corresponding Faraday current efficiency is 68.13%.

[0057] As can be seen from the above, the copper-based nanomaterials obtained by electrochemical deposition of doped halogen elements in this invention are rich in a large number of two-dimensional defects and dislocations, and have high selectivity and stability in electrocatalytic reduction of CO2 to generate multi-carbon products.

[0058] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing copper-based nanomaterials rich in two-dimensional defects, characterized in that: In the process of preparing copper-based nanomaterials by electrochemical deposition, copper-based nanomaterials rich in two-dimensional defects are obtained by inducing the formation of two-dimensional defects through halogen doping. The process includes the following steps: In an electrolytic cell with two electrodes, high-purity copper foil is used as the anode and carbon paper is used as the cathode. A potassium hydroxide solution with added halides is used as the electrolyte. A current of 170~210mA is applied and the reaction is carried out for 0.5~1 hour. Then the carbon paper is removed, cleaned, and dried to obtain copper-based nanomaterials rich in two-dimensional defects. F doping induces the formation of twin boundary defects and stacking fault defects in copper-based nanomaterials, Cl doping induces the formation of stacking fault defects in copper-based nanomaterials, and Br or I doping induces the formation of grain boundary defects in copper-based nanomaterials.

2. The method for preparing copper-based nanomaterials rich in two-dimensional defects according to claim 1, characterized in that: The concentration of potassium hydroxide solution is 1.0~4.0 mol / L.

3. The method for preparing a copper-based nanomaterial rich in two-dimensional defects according to claim 1, characterized in that: The concentration of halides in the electrolyte is 0.1~1.0 mol / L.

4. A copper-based nanomaterial rich in two-dimensional defects prepared by the preparation method according to any one of claims 1 to 3.

5. The application of the copper-based nanomaterial rich in two-dimensional defects as described in claim 4 in electrocatalytic CO2 reduction.

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